Automobile engines are required to meet the demands for better fuel economy and higher performance due to global environmental issues. As an engine part, high-functionality piston rings that enable good fuel economy and low oil consumption are sought after. Examples of such piston rings include inner rings and eccentric barrel face rings (BF ring).
FIGS. 5(a) and 5(b) show one example of an inner ring 1 and an eccentric BF ring 2, respectively.
The piston rings that have a top-bottom orientation such as these inner ring 1 and eccentric BF ring 2 can achieve their functions when their top-bottom orientation is correct. That is, these rings are designed to achieve required functions only when they are mounted to pistons in correct orientation. For example, the inner ring 1, when its inner surface 1a is on the upper side as shown in FIG. 5(a), can provide a good seal by the inner peripheral edge 1b on the lower side of the ring making high-pressure surface contact with the bottom surface of a ring groove (not shown), thereby preventing oil from traveling up into the combustion chamber through the backside of the ring. The inner ring 1 is contorted into a plate-like shape and fitted in the piston groove, and this state of being a plate-like shape provides the effect of preventing leakage of combustion gas, the effect of increasing compression ratio, and a wedge effect that allows easy spread of oil on the inner wall of the cylinder on the side of the combustion chamber. In other words, if the inner surface 1a is on the lower side, these effects cannot be achieved, and the engine performance may be deteriorated.
Piston rings, valve lifters, and other disk-like, cylindrical, or annular components that are sought after on the recent market have highly precise shape and dimensions because of their high-functionality. They are sometimes of a design that hardly allows visual determination of the top-bottom orientation, like the eccentric BF ring shown in FIG. 5(b), for example. These high-precision piston rings undergo complicated processing, where it is necessary to identify the orientation of the components not only in a process step of providing a marking or the like for identifying the top and bottom, but also in each of various process steps in manufacture. In the processing of disk-like, cylindrical, or annular components that have an orientation because of asymmetric upper and lower outer shapes such as piston rings, it is essential to keep the components oriented correctly during the processing.
The demands for high-functionality and high-precision components as mentioned above call for a simple method of identifying the top-bottom orientation of disk-like, cylindrical, or annular components that have asymmetric upper and lower outer shapes, for example eccentric BF rings, which hardly allow visual determination of the top and bottom, so that these components can always be oriented correctly all through the processing.